Objective:To investigate the rate of lumbar spinal stenosis complicated by lumbar instability and give some ideas for the choose of surgery. Methods:Ninty cases of lumbar spinal stenosis undergoing surgery in Zhong Da Hospital of Southeast University between 2008 and 2010 were investigated retrospectively。To measure angulation or segmental instability in flexion–extension X-rays according to Bambakidis NC.etc who diagnosed lumbar instability, and then analyse the result. Results: Lumbar spinal stenosis with instability in 47 patients with 59 segments, the total 59/139=42.5%, including 30 female cases and 17 male cases. The rate of lumbar instability in female is higher than male(P<0.05). Conclusion: The rate of Lumbar spinal stenosis with instability in segmental stenosis is 42.5%.Surgical internal fixation and bone graft fusion for the treatment of lumbar spinal stenosis complicated by lumbar instability is reasonable.